Novel Lumped-Distributed Planar Ring Resonator with Parallel-Coupled Feed

This paper presents a technique to design a lumped-distributed planar ring resonator based using quarter-wavelength parallel coupled feed lines. Lumped inductors are introduced for miniaturisation and to force the proposed circuit to resonate only at the fundamental mode. It is shown that the resonant frequency can be controlled by introducing capacitors into the ring section. The proposed circuit is designed and implemented with microstrip technology. From the simulated and measured results, a ring resonator operated in transmission mode resonates solely at 0.9 GHz and has an unloaded g-factor of 99.8. Moreover, the area of the designed circuit is reduced by 54%